Reinforced abrasive article mounted on a backing plate



REINFORCED ABRASIVE ARTICLE MOUNTED ON A BACKING PLATE Filed July- 1, 1943 3nnentor TM/Yaxwdf W/eddon LR.

(Ittorneg ham-emigrate REINFORCED ABRASIVE ARTICLE MOUNTED ON A BACKING PLATE William Maxweli Wheildon, In, Framingham, Mm, assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application July 1, 1943, Serial No. 492,992

2 Claims. (Cl. 51--209) This invention relates to'a reinforced abrasive article mounted on a backing plate, and more particularly to segment and disks which are mounted on steel backing plates and arranged for grinding on their flat faces.

Grinding disks and abrasive segments have been made heretofore of abrasive grains, such as crystalline alumina and silicon carbide, bonded by suitable bonds, such as magnesium oxychloride. This particular type of bond has certain desirable characteristics for grinding purposes,

but the bonded material may crack under the strains and stresses of the grinding operation;

hence it is desirable to reinforce the abrasive body by means of a wire mesh. Various problems have been presented in securing such an abrasive body on the metal backing disk which is mounted on the driven spindle of the machine. It has been found that when the abrasive material is secured to the metal by means of vulcanized rubber, the temperature of curing the rubber, which may be around 160 C., tends to damage the abrasive body. It has also been proposed to secure the abrasive body to a backing plate by means of screws inserted through the wire mesh and embedded in the abrasive, but the clamping pressure against the wire mesh or the abrasive sets up stresses that tend to weaken the wheel.

It is a primary object of this invention to overcome such problems and to provide a reinforced abrasive segment or grinding disk which is secured substantially integrally to a backing plate.

A further object of the invention is to provide a reinforced abrasive structure mounted on a metal backing plate in which the reinforcement is i rigidly secured to the backing plate and the surrounding abrasive is interlocked with and held securely in position by means of the reinforcement. Further objects will be apparent in the following disclosure.

In the accompanying drawing, which illustrates a preferred embodiment of my invention:

Fig. 1 is a perspective view, partly broken away, showing a set of abrasive segments permanently mounted on a steel plate; and

Fig. 2 is a fragmentary section through one of of the segments and its supporting plate.

In accordance with my invention, I propose to make an abrasive segment or an abrasive disk of a body of suitably bonded abrasive grains mounted on a metal plate and secured thereto by a reinforcing wire mesh which is in turn rigidly secured to the metal plate. The drawing shows a. plane faced grinding wheel made of a set of abrasive segments mounted on separate metal backing plates which are arranged as an annulus. on and secured to a single supporting metal disk. Each segment may comprise an abrasive body It mounted permanently on a steel plate I! and rigidly secured thereto by a reinforcing wire mesh It. A set of steel plates l2 and the associated abrasive bodies "are suitably shaped to provide.

an abrasive annulus having the top surfaces of the abrasive bodies lying in a plane. Each of the metal plates I2 is adapted to be mounted on a steel backingplate it which is in turn suitably connected to a'driving spindle It as by means of bolts passing through the bolt holes 20 of the plate and engaging a flanged head on the spindle.

The abrasive body may be made of a suitable material, such as silicon carbide or crystalline alumina grains, bonded by a suitable bond, such as magnesium oxychloride. The abrasive body may comprise various types of compositions. For

example, a satisfactory abrasive segment may be made of 45 pounds of crystalline alumina grains of desired grit size bonded into an integral mass by. means of a cement formed of 9.7 pounds of magnesia wetted by 5.7 pounds of an aqueous solution of magnesium chloride having a specific gravity of 1.l8.-This mass of grains and bond may be suitably mixed and tamped in a mold to form the abrasive body after which it is allowed to harden for a suitable period of time.

As a reinforcement, I proposed to employ a wire mesh or other equivalent foraminous or reticulated material. I prefer a wire cloth or an open mesh body known as expanded metal which is embedded in the abrasive mass and makes a strong reinforcement and provides many interlocking surfaces for holding the abrasive body in place. This wire mesh is embedded in the lower portion of the abrasive segment or disk as by placing it initially in the mold and tamping the mixture of grains and bond around the mesh. thus forming a rigid and substantially integral 1 body.

The primary feature of my invention comprises securing the wire mesh l4 rigidly to its backing plate l2 before the abrasive body is interlocked therewith. In the preferred construction, the wire mesh is welded directly to the steel plate l2 at suitably spaced points. This may be done by laying the wire mesh, such as an expanded metal sheet or a Woven wire cloth, on the steel plate l2; and then by suitable welding apparatus, such as an electric arc welder in which the electrode provides the needed welding metal, the wire mesh is integrally attached to the backing plate by the welding metal 22 deposited at a number of spaced II to the disk It. These are located in a suitable spacing, and they have their heads 25 countersunk in the backing'plate l2. The bolts project downwardly for insertion through suitable holes in the steel plate on which the segments are to be mounted and they are held in place by nuts 26. These bolts are put into place in the backing plate before the abrasive mass I is molded around the wire mesh. It will, therefore, be appreciated that the clamping or securing bolts 24 are independent of and lie wholly below the wire mesh and they do not engage it to any material extent, hence they cannot transmit any clamping stress to the wire mesh.

It will be observed that the abrasive body may be worn away down to the wire mesh since there are no obstructing members or securing devices above that wire mesh which can interfere with the grinding operation. This gives a maximum use of the abrasive for a given thickness of the body l0. The apertures in the expanded metal or wire screen, herein termed wire mesh, which is used for the reinforcement may be of any suitable size, such as 1" mesh or smaller. An expanded metal mesh with diamond shaped openings 1 x A" is suitable for an abrasive body which is a foot or larger in radial extent. .The number of spots of welding metal between the wire mesh and the metal plate I! may be as required to give a sufliciently rigid structure, but 25 or 30 welds are sumcient for an abrasive body of the above described size. The metal plate I! may be compartively thin such as A or inch, it being merely thick enough to hold the abrasive body rigidly in position and to clamp the same securely on the grlnding plate I. The wire mesh may be secured integrally to its backing plate by brazing or soldering it in position, and such procedure are to be considered as equivalents of the welding above described, it being evident that the method best suited for the construction will depend on the types of metals employed.

Various advantages in this construction will be readily apparent; and it will be appreciatedthat many modifications may be made in the construction without departing from the scope of the appended claims.

I claim:

1. A grinding wheel comprising a rotatable supporting plate, a metal backing plate, a wire mesh integrally secured directly to the backing plate surface by welding metal at spaced locations and havinglinterlocking portions therebetween, a body of bonded abrasive material molded on the plate and embedding and interlocking rigidly with said portions of the wire mesh, said welding metal holding the wire mesh and the abrasive permanentl immovable relative to the plate, and spaced fastening devices located beneath and independent of the wire mesh and molded body which secure the two plates together without imposing strain on said body.

2. A grinding wheel comprising a rotatable support, a, set of abrasive segments shaped to form an annulus for mounting on said support, each segment having a metal backing plate, a wire mesh integrally secured to each plate at spaced spots by welding metal, a body of bonded abrasive material permanently molded 0n the plate and embedding and interlocking rigidly with the wire mesh, and fastening devices independent of the abrasive bodies which removably secure the plates of said segments on the support.

WILLIAM MAXWELL WHEILDON, JR. 

